Calculates distance to the closest zero pixel for all non-zero pixels of source image.
Case 1: Not-in-place operations
IppStatus ippiDistanceTransform_3x3_<mod>(const Ipp8u* pSrc, int srcStep, Ipp<dstDatatype>* pDst, int dstStep, IppiSize roiSize, Ipp32s* pMetrics);
IppStatus ippiDistanceTransform_5x5_<mod>(const Ipp8u* pSrc, int srcStep, Ipp<dstDatatype>* pDst, int dstStep, IppiSize roiSize, Ipp32s* pMetrics);
Supported values for mod:
8u_C1R |
8u16u_C1R |
IppStatus ippiDistanceTransform_3x3_8u32f_C1R(const Ipp8u* pSrc, int srcStep, Ipp32f* pDst, int dstStep, IppiSize roiSize, Ipp32f* pMetrics);
IppStatus ippiDistanceTransform_5x5_8u32f_C1R(const Ipp8u* pSrc, int srcStep, Ipp32f* pDst, int dstStep, IppiSize roiSize, Ipp32f* pMetrics);
Case 2: In-place operations
IppStatus ippiDistanceTransform_3x3_8u_C1IR(Ipp8u* pSrcDst, int srcDstStep, IppiSize roiSize, Ipp32s* pMetrics);
IppStatus ippiDistanceTransform_5x5_8u_C1IR(Ipp8u* pSrcDst, int srcDstStep, IppiSize roiSize, Ipp32s* pMetrics);
The distance transform function ippiDistanceTransform is declared in the ippcv.h file. It operates with ROI (see Regions of Interest in Intel IPP).
This function approximates the actual distance from the closest zero pixel to each certain pixel with the sum of atomic distances from the fixed set. The set consists of two values for a 3x3 mask and three values for a 5x5 mask.
Figure “3x3 Mask” shows the result of the distance transform of a 7x7 image with zero point in the center. This example corresponds to a 3x3 mask. Two numbers specify metrics in case of the 3x3 mask:
In this case the values are 1 and 1.5 correspondingly.
| 4.5 | 4 | 3.5 | 3 | 3.5 | 4 | 4.5 |
| 4 | 3 | 2.5 | 2 | 2.5 | 3 | 4 |
| 3.5 | 2.5 | 1.5 | 1 | 1.5 | 2.5 | 3.5 |
| 3 | 2 | 1 | 0 | 1 | 2 | 3 |
| 3.5 | 2.5 | 1.5 | 1 | 1.5 | 2.5 | 3.5 |
| 4 | 3 | 2.5 | 2 | 2.5 | 3 | 4 |
| 4.5 | 4 | 3.5 | 3 | 3.5 | 4 | 4.5 |
Figure “5x5 Mask” shows the distance transform for the same image, but for a 5x5 mask.
For this mask yet another number is added to specify metrics - the additional distance, i.e., the distance between pixels corresponding to the chess knight move.
In this example, the additional distance is equal to 2.
| 4 | 3.5 | 3 | 3 | 3 | 3.5 | 4 |
| 3.5 | 3 | 2 | 2 | 2 | 3 | 3.5 |
| 3 | 2 | 1.5 | 1 | 1.5 | 2 | 3 |
| 3 | 2 | 1 | 0 | 1 | 2 | 3 |
| 3 | 2 | 1.5 | 1 | 1.5 | 2 | 3 |
| 3.5 | 3 | 2 | 2 | 2 | 3 | 3.5 |
| 4 | 3.5 | 3 | 3 | 3 | 3.5 | 4 |
Example “Using the function ippiDistanceTransform_3x3” shows how to use the function ippiDistanceTransform_3x3_8u_C1R.
ippStsNoErr |
Indicates no error. Any other value indicates an error or a warning. |
ippStsNullPtrErr |
Indicates an error condition if one of the specified pointers is NULL. |
ippStsSizeErr |
Indicates an error condition if roiSize has a field with zero or negative value. |
ippStsStepErr |
Indicates an error condition if srcStep or dstStep is less than roiSize.width*<pixelSize>. |
ippStsNotEvenStepErr |
Indicates an error condition if step value is not divisible by 2 for 16u images, and by 4 for 32f images. |
ippStsCoeffErr |
Indicates an error condition if at least one element of pMetrics array has zero or negative value. |
Ipp8u
src[7*7] = {
1, 2, 3, 4, 5, 6, 7,
1, 0, 3, 4, 5, 6, 7,
1, 2, 3, 4, 5, 6, 7,
1, 2, 3, 0, 5, 6, 7,
1, 2, 3, 4, 5, 6, 7,
1, 2, 3, 4, 5, 0, 7,
1, 2, 3, 4, 5, 6, 7
};
Ipp8u dst[7*7];
IppiSize roiSize = { 7, 7 };
Ipp32s pMetrics[2] = { 2, 2 };
ippiDistanceTransform_3x3_8u_C1R ( src, 7, dst, 7, roiSize, pMetrics );
result:
1 2 3 4 5 6 7
1 0 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 0 5 6 7 src
1 2 3 4 5 6 7
1 2 3 4 5 0 7
1 2 3 4 5 6 7
2 2 2 4 6 6 6
2 0 2 4 4 4 6
2 2 2 2 2 4 6
4 4 2 0 2 4 4 dst
6 4 2 2 2 2 2
6 4 4 4 2 0 2
6 6 6 4 2 2 2
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